bool CheckGrammar(out string reason)
{
reason = string.Empty;
// First Rule cannot be intermediate.
if (ProductionRules.First().IsIntermediate)
{
reason = "First rule cannot be marked as intermediate.";
return(false);
}
// All Rule.Name UNION Terminal.Name Must be unique
var allNames = ProductionRules.Select(pr => pr.Name).Union(TerminalSymbols.Select(ts => ts.Name));
var duplicateNames = allNames.GroupBy(s => s).Where(g => g.Count() > 1);
if (duplicateNames.Any())
{
reason = "Duplicate names: " + string.Join(", ", duplicateNames.Select(duplicateName => duplicateName.Key));
return(false);
}
// Each Rule should have a Non Null "Group" as the RHS - ie Produces has been called
var nullRhsProductionRuleNames = ProductionRules.Where(pr => pr.Rhs == null || pr.Rhs.Count == 0).Select(pr => pr.Name);
if (nullRhsProductionRuleNames.Any())
{
reason = "Rules which don't produce anything: " + string.Join(", ", nullRhsProductionRuleNames);
return(false);
}
// A 'target' (i.e element of a RulePart) must exist in the list of Rule.Name UNION Terminal.Name
var badTargetRuleNames = ProductionRules.Where(pr => pr.Rhs.Any(rp => rp.AsEnumerable().Any(target => !allNames.Contains(target.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).First())))).Select(r => r.Name);;
if (badTargetRuleNames.Any())
{
reason = "Rules which produce unknown targets: " + string.Join(", ", badTargetRuleNames);
return(false);
}
// A RuleOrTerminal should not have a RulePart where the first RuleOrTerminal is the rule.
var directLeftRecursion = ProductionRules.Where(r => r.Rhs.AsEnumerable().Where(rp => rp.Count() > 0 && rp[0] == r.Name).Any());
if (directLeftRecursion.Any())
{
reason = "Direct left recursion: " + string.Join(", ", directLeftRecursion);
return(false);
}
return(true);
}
public override string ToString()
{
StringBuilder result = new StringBuilder();
TerminalSymbols.ForEach(symbol =>
{
if (symbol != Helper.IdentitySymbol && symbol != Helper.EmptySymbol)
{
result.Append(String.Format("{0}, ", symbol));
}
});
result.Remove(result.Length - 2, 2);
result.Append(";" + Environment.NewLine);
NonterminalSymbols.ForEach(symbol => result.Append(String.Format("{0}, ", symbol)));
result.Remove(result.Length - 2, 2);
result.Append(";" + Environment.NewLine);
result.Append(Rules.GetString());
result.Append(";" + Environment.NewLine);
result.Append(StartSymbol);
return(result.ToString());
}
